Kerry: GOP's Iran Letter 'Absolutely Calculated To Interfere With Negotiations'

"It's unprecedented."

On CBS' Face the Nation Sunday, Secretary of State John Kerry railed against Republicans for drafting and signing a letter to Iran amidst nuclear negotiations with President Obama.

"This letter was absolutely calculated directly to interfere with these negotiations," Kerry told Margaret Brennan during the interview. "It specifically inserts itself directly to the leader of another country, saying, 'Don't negotiate with these guys, because we're going to change this.'"

Kerry asserted that the GOP's actions were unconstitutional -- "with respect to the executive's right to negotiate" -- and also "incorrect, because they cannot change an executive agreement."

"That's unprecedented, unprecedented," Kerry said dramatically. He added, "It's false information and directly calculated to interfere, and basically say, 'Don't negotiate with them, you've got to negotiate with 535 members of Congress.'"

Brennan interjected, "They have to negotiate with you, you're the one that has to sit at that table."

Kerry responded:

Well, I understand, but it's unprecedented, I've never seen anything like this. Now in fairness, look, I don't know how many people, you know, really focus completely on it, but I do know that the effect and the intent of the author was to basically say, 'Don't do this deal.' And by the way, that's to say that, before there even is a deal. I mean it's like, you know, giving people a grade on a test before the test is even written let alone given. It's wrong, it's unprecedented, and I hope it hasn't made it very difficult here.

Kerry made it clear that he would not issue an apology to the Iranian government because of the letter. "Not on your life," the secretary said.

Brennan did not ask Kerry about the time he flew to the capital city of Nicaragua and accused Ronald Reagan of engaging with terrorism while a senator during that administration.